PDF417 TWO-DIMENSIONAL code knowledge introduction

　　PDF417 TWO-DIMENSIONAL code is a kind of multi-layer, variable length, with high data volume and error correction ability of continuous layer of two-dimensional bar code. Each PDF417 QR code symbol can represent 1100 bytes of information, or 1800 ASCII characters or 2700 numbers. PDF (PORTABLE DATA FILE) because each symbol character of the bar code is composed of 4 bars and 4 blanks, if the narrowest bar or blank of the bar code is called a module, the total number of modules of the 4 bars and 4 blanks must be 17. So it's called 417 code or PDF417 code.

　　First, PDF417 two-dimensional code symbol structure

　　PDF417 QR code symbol is a multi-line structure, consisting of a sequence of lines surrounded by blank space. The top and bottom of the symbol are blank Spaces, and the left and right Spaces are left and right Spaces respectively. Multiple lines of structure between upper and lower white space. Each line of data symbol has the same number of characters.

　　The minimum number of rows is 3 and the maximum is 90. Each line consists of a left margin, a start character, a left indicator character, a right indicator character, a terminator, and a right margin. Since the number of lines and the number of symbols in each line is variable, the ratio of height and width of PDF417 qr code symbols is variable.

　　Features of PDF417 QR code

　　PDF417 QR code is mainly used for transportation, laboratory slip, ID card and inventory management, etc. (The PDF 417 symbol system is mainly used in Europe and The United States, The 2d barcode symbol system is mainly used in logistics applications (especially in The automotive industry), transportation systems (such as shipping labels), identification (such as driving licenses, passports) and document management.)

　　Printing requirements are not high, ordinary printing equipment can be printed, fax can also be read. Error correction capability One-dimensional codes usually have a check function to prevent misreading. Once the bar code is defaced, it will be rejected. The TWO-DIMENSIONAL code can not only prevent errors, but also correct errors, even if the bar code part damage, also can restore the correct information.